# Strontium Electron Configuration

The electron configuration of strontium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 or [Kr] 5s2.

Contents

## Methods

We can write the electron configuration of strontium using four different methods:

#1 Using aufbau principle
#2 Using periodic table
#3 From its bohr model
#4 From its orbital diagram

Let’s break down each method in detail.

### #1 Using Aufbau Principle

• First, find electrons of strontium atom

The atomic number of strontium represents the total number of electrons of strontium. Since the atomic number of strontium is 38, the total electrons of strontium are 38.

• Second, make a table of subshell and its maximum electrons

Calculate the maximum number of electrons each subshell can hold using the formula: 4ℓ + 2

Where, ℓ = azimuthal quantum number of the subshell

For s subshell, ℓ = 0
For p subshell, ℓ = 1
For d subshell, ℓ = 2
For f subshell, ℓ = 3

 subshell max. electrons s 2 p 6 d 10 f 14

This means that,

Each s subshell can hold maximum 2 electrons
Each p subshell can hold maximum 6 electrons
Each d subshell can hold maximum 10 electrons
Each f subshell can hold maximum 14 electrons

• Finally, use aufbau chart and start writing electron configuration

Remember that we have a total of 38 electrons.

According to the aufbau principle, 1s subshell is filled first and then 2s, 2p, 3s… and so on.

By looking at the chart, you can see that electrons are first filled in 1s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 1s subshell.

So the electron configuration will be 1s2. Where, 1s2 indicates that the 1s subshell has 2 electrons.

Now we have used 2 electrons in the 1s subshell, so we have a total of 38 – 2 = 36 electrons left.

Looking at the chart, after 1s subshell now comes 2s subshell. Again, each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 2s subshell.

So the electron configuration will be 1s2 2s2. Where, 2s2 indicates that the 2s subshell has 2 electrons.

Again, we have used 2 electrons in the 2s subshell, so we have a total of 36 – 2 = 34 electrons left.

After 2s subshell now comes 2p subshell. Each p-subshell can hold a maximum of 6 electrons, so we will use 6 electrons for the 2p subshell.

So the electron configuration will be 1s2 2s2 2p6. Where, 2p6 indicates that the 2p subshell has 6 electrons.

Here, we have used 6 electrons in the 2p subshell, so we have a total of 34 – 6 = 28 electrons left.

After 2p subshell now comes 3s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 3s subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2. Where, 3s2 indicates that the 3s subshell has 2 electrons.

Here, we have used 2 electrons in the 3s subshell, so we have a total of 28 – 2 = 26 electrons left.

After 3s subshell now comes 3p subshell. Each p-subshell can hold a maximum of 6 electrons, so we will use 6 electrons for the 3p subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6. Where, 3p6 indicates that the 3p subshell has 6 electrons.

Here, we have used 6 electrons in the 3p subshell, so we have a total of 26 – 6 = 20 electrons left.

After the 3p subshell now comes 4s subshell. Each s-subshell can hold a maximum of 2 electrons, so we will use 2 electrons for the 4s subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2. Where, 4s2 indicates that the 4s subshell has 2 electrons.

Here, we have used 2 electrons in the 4s subshell, so we have a total of 20 – 2 = 18 electrons left.

After 4s subshell now comes 3d subshell. Each d-subshell can hold a maximum of 10 electrons, so we will use 10 electrons for the 3d subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10. Where, 3d10 indicates that the 3d subshell has 10 electrons.

Here, we have used 10 electrons in the 3d subshell, so we have a total of 18 – 10 = 8 electrons left.

After the 3d subshell now comes the 4p subshell. Each p-subshell can hold a maximum of 6 electrons, so we will use 6 electrons for the 4p subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6. Where, 4p6 indicates that the 4p subshell has 6 electrons.

Here, we have used 6 electrons in the 4p subshell, so we have a total of 8 – 6 = 2 electrons left.

After 4p subshell now comes 5s subshell. Each s-subshell can hold a maximum of 2 electrons, and we also have 2 electrons left, so we will use that 2 electrons for the 5s subshell.

So the electron configuration will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2. Where, 5s2 indicates that the 5s subshell has 2 electrons.

Therefore, the final electron configuration of strontium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2. And the condensed/abbreviated electron configuration of strontium is [Kr] 5s2.

Where, Kr is krypton

### #2 Using Periodic Table

• First, get periodic table chart with spdf notation

The above image shows periodic table blocks.

The ‘s’ in s block represents that all s block elements have their valence electrons in s subshell. Similarly, the ‘p’ in p block represents that all p block elements have their valence electrons in p subshell. And so on for d block and f block.

• Second, mark location of strontium on periodic table

Strontium is the s block element located in group 2 and period 5. Hence, mark the location of strontium on the periodic table as follows:

• Finally, start writing electron configuration

Remember that: each s subshell can hold maximum 2 electrons, each p subshell can hold maximum 6 electrons, each d subshell can hold maximum 10 electrons, and each f subshell can hold maximum 14 electrons.

Start writing electron configuration from the very first element (i.e., hydrogen) all the way up to strontium.

So the electron configuration of strontium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2.

### #3 From its Bohr Model

In the above image, 1 represents the 1st electron shell. Similarly, 2 represents the 2nd electron shell, 3 represents the 3rd electron shell, 4 represents the 4th electron shell, and 5 represents the 5th electron shell.

The 1st electron shell contains 1s subshell, the 2nd electron shell contains 2s and 2p subshells, the 3rd electron shell contains 3s, 3p, and 3d subshells, the 4th electron shell contains 4s and 4p subshells, and the 5th electron shell contains 5s subshell.

We know that each s subshell can hold maximum 2 electrons, each p subshell can hold maximum 6 electrons, each d subshell can hold maximum 10 electrons, and each f subshell can hold maximum 14 electrons.

Also, we have to make sure that the electron configuration will match the order of aufbau principle (i.e., the 1s subshell is filled first and then 2s, 2p, 3s… and so on).

So the electron configuration of strontium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2.

Where,

1s2 indicates that the 1s subshell has 2 electrons.
2s2 indicates that the 2s subshell has 2 electrons.
2p6 indicates that the 2p subshell has 6 electrons.
3s2 indicates that the 3s subshell has 2 electrons.
3p6 indicates that the 3p subshell has 6 electrons.
4s2 indicates that the 4s subshell has 2 electrons.
3d10 indicates that the 3d subshell has 10 electrons.
4p6 indicates that the 4p subshell has 6 electrons.
5s2 indicates that the 5s subshell has 2 electrons.

Learn how to draw: Strontium Bohr Model

### #4 From its Orbital Diagram

The above orbital diagram shows that the 1s subshell has 2 electrons, the 2s subshell has 2 electrons, the 2p subshell has 6 electrons, the 3s subshell has 2 electrons, the 3p subshell has 6 electrons, the 4s subshell has 2 electrons, the 3d subshell has 10 electrons, the 4p subshell has 6 electrons, and the 5s subshell has 2 electrons.

So the electron configuration of strontium will be 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2.

Learn how to draw: Strontium Orbital Diagram

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